Bispecific or multispecific antibodies have been generated in attempts to prepare molecules useful for the treatment of various inflammatory diseases, cancers, and other disorders.
Bispecific antibodies have been produced using the quadroma technology (see Milstein, C. and A. C. Cuello, Nature, 1983. 305(5934): p. 537-40) based on the somatic fusion of two different hybridoma cell lines expressing murine monoclonal antibodies with the desired specificities of the bispecific antibody. Bispecific antibodies can also be produced by chemical conjugation of two different mAbs (see Staerz, U. D., et al., Nature, 1985. 314(6012): p. 628-31). Other approaches have used chemical conjugation of two different monoclonal antibodies or smaller antibody fragments (see Brennan, M., et al., Science, 1985. 229(4708): p. 81-3).
Another method is the coupling of two parental antibodies with a hetero-bifunctional crosslinker. In particular, two different Fab fragments have been chemically crosslinked at their hinge cysteine residues in a site-directed manner (see Glennie, M. J., et al., J Immunol, 1987. 139(7): p. 2367-75).
Other recombinant bispecific antibody formats have been developed in the recent past (see Kriangkum, J., et al., Biomol Eng, 2001. 18(2): p. 31-40). Amongst them tandem single-chain Fv molecules and diabodies, and various derivatives thereof, have been used for the construction of recombinant bispecific antibodies. Normally, construction of these molecules starts from two single-chain Fv (scFv) fragments that recognize different antigens (see Economides, A. N., et al., Nat Med, 2003. 9(1): p. 47-52). Tandem scFv molecules (taFv) represent a straightforward format simply connecting the two scFv molecules with an additional peptide linker. The two scFv fragments present in these tandem scFv molecules form separate folding entities. Various linkers can be used to connect the two scFv fragments and linkers with a length of up to 63 residues (see Nakanishi, K., et al. Annu Rev Immunol, 2001. 19: p. 423-74).
In a recent study, in vivo expression by transgenic rabbits and cattle of a tandem scFv directed against CD28 and a melanoma-associated proteoglycan was reported (see Gracie, J. A., et al., J Clin Invest, 1999. 104(10): p. 1393-401). In this construct the two scFv molecules were connected by a CH1 linker and serum concentrations of up to 100 mg/L of the bispecific antibody were found. A few studies have now reported expression of soluble tandem scFv molecules in bacteria (see Leung, B. P., et al., J Immunol, 2000. 164(12): p. 6495-502; Ito, A., et al., J Immunol, 2003. 170(9): p. 4802-9; Karni, A., et al., J Neuroimmunol, 2002. 125(1-2): p. 134-40) using either a very short Ala3 linker or long glycine/serine-rich linkers.
In a recent study, phage display of a tandem scFv repertoire containing randomized middle linkers with a length of 3 or 6 residues enriched those molecules which are produced in soluble and active form in bacteria. This approach resulted in the isolation of a preferred tandem scFv molecule with a 6 amino acid residue linker (see Arndt, M. and J. Krauss, Methods Mol Biol, 2003. 207: p. 305-21).
Bispecific diabodies (Db) utilize the diabody format for expression. Diabodies are produced from scFv fragments by reducing the length of the linker connecting the VH and VL domain to approximately 5 residues (see Peipp, M. and T. Valerius, Biochem Soc Trans, 2002. 30(4): p. 507-11). This reduction of linker size facilitates dimerization of two polypeptide chains by crossover pairing of the VH and VL domains. Bispecific diabodies are produced by expressing two polypeptide chains with either the structure VHA-VLB and VHB-VLA (VH-VL configuration) or VLA-VHB and VLB-VHA (VL-VH configuration) within the same cell. A recent comparative study demonstrates that the orientation of the variable domains can influence expression and formation of active binding sites (see Mack, M., G. Riethmuller, and P. Kufer, Proc Natl Acad Sci USA, 1995. 92(15): p. 7021-5).
One approach to force the generation of bispecific diabodies is the production of knob-into-hole diabodies (see Holliger, P., T. Prospero, and G. Winter, Proc Natl Acad Sci USA, 1993. 90(14): p. 6444-8.18). This was demonstrated for a bispecific diabody directed against HER2 and CD3. A large knob was introduced in the VH domain by exchanging Va137 with Phe and Leu45 with Trp and a complementary hole was produced in the VL domain by mutating Phe98 to Met and Tyr87 to Ala, either in the anti-HER2 or the anti-CD3 variable domains. By using this approach the production of bispecific diabodies could be increased from 72% by the parental diabody to over 90% by the knob-into-hole diabody.
Single-chain diabodies (scDb) represent an alternative strategy to improve the formation of bispecific diabody-like molecules (see Holliger, P. and G. Winter, Cancer Immunol Immunother, 1997. 45(3-4): p. 128-30; Wu, A. M., et al., Immunotechnology, 1996. 2(1): p. 21-36). Bispecific single-chain diabodies are produced by connecting the two diabody-forming polypeptide chains with an additional middle linker with a length of approximately 15 amino acid residues. Consequently, all molecules with a molecular weight corresponding to monomeric single-chain diabodies (50-60 kDa) are bispecific. Several studies have demonstrated that bispecific single chain diabodies are expressed in bacteria in soluble and active form with the majority of purified molecules present as monomers (see Holliger, P. and G. Winter, Cancer Immunol Immunother, 1997. 45(3-4): p. 128-30; Wu, A. M., et al., Immunotechnology, 1996. 2(1): p. 21-36; Pluckthun, A. and P. Pack, Immunotechnology, 1997. 3(2): p. 83-105; Ridgway, J. B., et al., Protein Eng, 1996. 9(7): p. 617-21).
Diabody have been fused to Fc to generate more Ig-like molecules, named di-diabody (see Lu, D., et al., J Biol Chem, 2004. 279(4): p. 2856-65). In addition, multivalent antibody construct comprising two Fab repeats in the heavy chain of an IgG and capable of binding four antigen molecules has been described (see U.S. Pat. No. 8,722,859 B2, and Miller, K., et al., J Immunol, 2003. 170(9): p. 4854-61).
The most recent examples are tetravalent IgG-single-chain variable fragment (scFv) fusions (Dong J, et al. 2011 MAbs 3:273-288; Coloma M J, Morrison S L 1997 Nat Biotechnol 15:159-163; Lu D, et al. 2002 J Immunol Methods 267:213-226), catumaxomab, a trifunctional rat/mouse hybrid bispecific epithelial cell adhesion molecule-CD3 antibody (Lindhofer H, et al 1995 J Immunol 155:219-225), the bispecific CD19-CD3 scFv antibody blinatumomab (Bargou R, et al. 2008 Science 321:974-977), “dual-acting Fab” (DAF) antibodies (Bostrom J, et al. 2009 Science 323:1610-1614), covalently linked pharmacophore peptides to catalytic anti-bodies (Doppalapudi V R, et al. 2010 Proc Natl Acad Sci USA 107:22611-22616), use of the dynamic exchange between half IgG4 molecules to generate bispecific antibodies (van der Neut Kolfschoten M, et al. 2007 Science 317:1554-1557; Stubenrauch K, et al. 2010 Drug Metab Dispos 38:84-91), or by exchange of heavy-chain and light-chain domains within the antigen binding fragment (Fab) of one half of the bispecific antibody (CrossMab format) (Schaefer W et al 2011 Proc Natl Acad Sci 108:11187-92).
There is a need in the art for single molecular entities with dual antigen binding function, and for methods of generating such multivalent and multispecific binding proteins. The present invention addresses these and other needs.